The present invention relates to passive thin film devices that compensate for signal losses over trace conductors at printed circuit assemblies and/or connectors and/or transmission lines and passively augment the impedance characteristic of the relevant conductive pathway, among other applications.
Dielectric and conductor losses, cross talk, reflections and noise, among a variety of other parasitic and signal degrading conditions, can impair operation of high frequency digital circuits, such as used in many telecommunication and networking applications. These problems are especially apparent at frequencies and data transfer rates in excess of 1.0 GHz, where reduced performance means reduced bandwidth and more hardware to achieve any desired result.
Cross talk can develop between signal lines and reflections and noise can develop from terminations. The resultant losses or signal attenuation, noise and cross talk can distort and reduce the fidelity of transmitted data signals. Delays can also occur with a resultant loss of synchronization in data conveyed between data supply conductors and responding circuitry. The degradation of signal fidelity and loss of synchronization make it difficult to distinguish the information content of transmitted data. High frequency circuit designers therefore expend considerable effort to minimize sources of noise, cross talk and signal attenuation.
Optical fiber, active repeater/amplifier devices and/or special materials can be used to improve signal integrity. Such devices, however, frequently require increased power and increased physical space for the circuitry. These improvements can also be relatively costly to implement.
Passive devices, such as capacitors or simple RC circuits, have been mounted to the top and bottom surfaces of printed circuit boards in close association to populated circuitry to enhance signal quality. Such mountings can be costly to implement and cannot be readily re-worked, if changes or fine-tuning is required. Embedded capacitors have also been incorporated into integrated circuit packages as shown at U.S. Pat. No. 6,407,929.
The subject invention provides thin film devices or equalization modules constructed of planar copper component features (e.g. passive resistors, capacitors, inductors) and/or hybrid components that, for example, can be coupled to printed circuit assemblies (e.g. mother and daughter boards) to offset losses present in signal carrying conductors. The equalization modules can be coupled to individual trace conductors of a printed circuit assembly to provide a tailored impedance characteristic to passively compensate for inherent high frequency signal degradation. The modules can also be mounted in connectors that couple to a printed circuit assembly to compensate for anticipated high frequency losses over a designed bandwidth at selected trace conductors at the pc board. Improved signal fidelity and synchronization are thereby achieved over an expanded operational bandwidth